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I have 1998 Honda Civic Lx 5spd 265,000 miles all factory no mods. Im at aloss to fix this isuue that started a couple months ago it started with a low rough idle after warm up around 200-500 rpms never stalled although it seemed like it would. About a month later the cel came on and idle went up to 1500-1700 rpms and sputters between the two,also when trying to drive like this in 1st and sometimes 2nd gear it jerks and bucks wildly until above that rpm range,when pushing in the clutch or letting off the throttle it jerks kinda like when u pop it out of gear without using the clutch. I checked the cel code it was the iacv i bought a new one from a honda dealership and seemed to correct the problem for a few days then i was sitting at idle at a stop light and the cel came back on with all the same problems as before as well as cel said the iacv again. So i checked everything plugs,cap,button,wires was all replaced about 6 months ago but checked anyways ignition part looked great,coolant is great,checked for vacuum leaks found none,when i replaced the iacv i cleaned the throttle body really good as well. So i thought maybe i got a bad iacv so replaced it with another one from the dealership,made sure everything was clean and good to go. Cleared the cel again and same thing a few days later while sitting at idle after warm up,cel came on and idle goes to 1500-1700 rpms with all the same symptoms as before. Once again cel says the iacv and that is the ONLY code it is throwing. I am at a loss and frustrated,this has been a great car to me as ive been great to it with its service maintenance i have had this civic for all but 12yrs. Any suggestions or help PLEASE!!!!!!